A new technique for tokamak edge density measurement based on microwave interferometer

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic techniques

Background:

• Accurate plasma density measurements are crucial for understanding and controlling fusion devices.
• Existing methods may have limitations in edge plasma diagnostics.

Purpose of the Study:

• To present a novel diagnostic technique, Microwave Interferometer in the Limiter Shadow (MILS), for measuring plasma density at the edge of hot plasma devices.
• To develop and validate a 3D synthetic diagnostic model and a reconstruction algorithm for MILS.

Main Methods:

• Utilizing a microwave beam passing tangentially through the edge plasma, measuring phase and power changes.
• Developing a 3D model as a synthetic diagnostic to explore wave propagation regimes.
• Implementing a genetic algorithm (genMILS) for density profile reconstruction based on a synthetic measurement database.

Main Results:

• The MILS diagnostic concept was evaluated on the ASDEX Upgrade tokamak, suitable for densities from 10^15 to 10^19 m^-3.
• The genMILS algorithm achieved low density reconstruction errors, estimated at 5% to 15% for densities >= 10^17 m^-3.
• The study demonstrated the potential for accurate density estimation, largely dependent on experimental uncertainties.

Conclusions:

• The MILS diagnostic technique, coupled with the genMILS algorithm, offers a promising approach for accurate edge plasma density measurements.
• The diagnostic is adaptable to various conditions and plasma parameters.
• Further refinement will focus on minimizing experimental uncertainties to maximize density estimation accuracy.